Conventional radiation diagnostic apparatuses, such as an X-ray computed tomography (CT) apparatus, include a radiation detector that detects radiation, such as X-rays and γ rays. The radiation diagnostic apparatus generally includes a collimator that eliminates scattered radiation from radiation that is incident on the radiation detector. The collimator includes a one-dimensional collimator that eliminates scattered radiation from a channel direction and a two-dimensional collimator that eliminates scattered radiation from the channel direction and a slice direction (body axis direction).
Conventionally, by creating a collimator as a seamless assembly, a one-dimensional collimator is manufactured such that the thickness and pitch of its collimator plates are uniform. In contrast, for a two-dimensional collimator, because it is necessary to arrange collimator plates in two-dimensional directions, it is difficult to create a collimator for all the channels and slices as a seamless assembly. For this reason, for the two-dimensional collimator, a manufacturing method is used in which a plurality of collimator modules are created and arranged so as to be aligned in the channel direction and the slice direction.
However, in the conventional technology in which a plurality of collimator modules are arranged so as to be aligned, the thickness and pitch of the collimator plates are not always uniform. FIGS. 20 to 23 illustrate the problem in the conventional technology.
For example, when collimator modules 10 each with outer frames on all four sides, as shown in FIG. 20, are aligned, the thickness and pitch of the collimator plates are discontinuous in the channel direction (indicated by the arrow C) and the slice direction (indicated by the arrow S) in positions where collimator modules meet. Furthermore, for example, when collimator modules 20, as shown in FIGS. 22 and 23, each with outer frames on two sides are aligned such that the ends of the collimator plates, which are ends protruding on the sides with no outer frame, make contact with outer frames of adjacent modules, the pitch may be inconsistent between the modules due to manufacturing errors. The pitch error increases as the number of modules to be combined increases. As described above, in the conventional technology, the thickness and pitch of the collimator plates are not always uniform.